In manufacturing electronic devices, by performing an etching process on a silicon oxide film serving as an insulating layer, holes or trenches are formed therein. In etching the silicon oxide film, generally, a target object is exposed to plasma of a fluorocarbon gas, so that the silicon oxide film is etched as described in Patent Document 1.
In the etching process with plasma of the fluorocarbon gas, the silicon oxide film is etched by active species of fluorine. Further, in the etching process, fluorocarbon is deposited on the silicon oxide film to form a deposit thereon.
Patent Document 1: Specification of U.S. Pat. No. 7,708,859
In the etching process on the silicon oxide film as described above, a film thickness of the deposit gradually increases. The increase in the film thickness of the deposit suppresses active species capable of etching the silicon oxide film from reaching the silicon oxide film. As a result, the etching process on the silicon oxide film is stopped on the way. Accordingly, an etching rate of the silicon oxide film is decreased.
Therefore, in order to continuously perform the etching process on the silicon oxide film, a new etching method is needed.